In a LTE (Long term Evolution) and previous wireless communication system, a cell only has a carrier (or a pair of carriers) generally, and a UE (User Equipment) can only receive and send data in a cell (on the carrier or carriers) at the same time.
FIG. 1 shows a schematic diagram of carrier bandwidth in a current LTE system. In the LTE system, the maximum bandwidth of a carrier is 20 MHz.
With the development of communication technology, an LTE-A (Long Term Evolution Advanced) system has great improvement on peak rate compared with an LTE system, and is required to reach 1 Gbps downlink and 500 Mbps uplink. Obviously, the transmission bandwidth of 20 MHz has been unable to meet such demand. Besides higher requirements on transmission rate, the LTE-A system needs better compatibility with the LTE system. In consideration of the improved peak rate, compatibility with the LTE system and full use of spectrum resource, a CA (Carrier Aggregation) technique is introduced in the LTE-A system, viz. the UE can aggregate a plurality of component carriers at the same time and transmit data on the carriers at the same time so as to improve data transmission rate.
To ensure that a UE of the LTE system can work under each aggregated carrier, each carrier is set to be no more than 20 MHz. Each component carrier in the LTE-A system is compatible with LTE Rel-8.
FIG. 2 shows a schematic diagram of the CA technique in a current LTE-A system.
In the LTE-A system shown in FIG. 2, the UE can aggregate 4 carriers. A Network side can transmit data with the UE on 4 carriers at the same time.
Furthermore, FIG. 3 shows a schematic diagram for a network structure of a current system including an RN (Relay Node); wherein, an eNB (evolved NodeB) is connected to a core network (CN) through a wire interface, the RN is connected to a DeNB (Donor eNB) through a wireless interface, an R-UE is connected to the RN through the wireless interface (Uu interface).
In prior art, the RN can be divided into the following types according to type of a relay data package:
L1 RN (Layer 1 Relay Node);
L2 RN (Layer 2 Relay Node);
L3 RN (Layer 3 Relay Node).
Wherein, the L3 RN can be divided into the following two kinds according to that whether it is necessary to divide carrier resource on time domain:
The RN requiring resource division;
The RN not requiring resource division;
It should be noted that the RN Type mentioned in follow-up description of embodiments of the present invention is the RN requiring or not requiring resource division.
The RN requiring resource division cannot receive and send at Uu interface and Un interface at the same time, otherwise self-interference will be caused. To avoid self-interference, a solution is to create ‘gaps’ in downlink access transmission time of an R-UE of the Uu interface. The gap can be used for a DL BH Link (Downlink Backhaul Link), viz. a downlink BH subframe. ‘Gaps’ configuration can be realized through a MBSFN (Multicast Broadcast Single Frequency Network) subframe.
FIG. 4 shows a schematic diagram for relay link downlink transmission at the Un interface by using the MBSFN subframe in the prior art. In these ‘gaps’, downlink transmission will be performed between the DeNB and the RN rather than between the RN and the R-UE.
Furthermore, RN starting process of the current network including RN is divided into the following two phase:
Phase I: the RN works as an UE access network. The specific process flow is as follows.
The RN is attached to a network in the same manner as an UE. The RN downloads initial configuration information from RN OAM, including a Donor Cell list allowable for connection, and then is attached.
Phase II: the RN works as an RN access network. The specific process flow is as follows.
First, the RN selects the Donor cell, the RN selects a Donor cell from the Donor cell list provided in Phase I.
Then a MME is selected for the RN: the RN informs the DeNB the identity of the RN through a RRC signaling during attachment. The DeNB selects a MME supporting the RN for the RN based on the information;
A GW is selected for the RN: the MME selects the DeNB as a P/S-GW of the RN after a CN informs the MME that the access node is the RN;
Corresponding S1 and X2 interfaces are recommended between the RN and the DeNB: the RN launches the process of establishing S1 and X2 on a bear built by the DeNB.
In the prior technical solution, L3 RN type is determined with the methods as below: If the application of CA for the Un interface is not taken into account in R10 edition of 3GPP LTE-A specification, RN type is determined by RN realization in a possible manner as below:
The RN acquires the cell supported by a RN Uu interface from a RN OAM;
The RN determines the cell used by the Un interface according to the donor cell accessed;
The RN determines the RN type according to the cell supported by the Uu and Un interface and software and hardware capacity of the RN (whether resource division is required);
The RN indicates type of the RN to the DeNB through a 1 bit indication.
In the prior technical solution, RN type can be indicated in two manners as below. The specific manner has not been decided.
Alt1: RAN type is carried in a RRC connection complete message;
Alt2: independent RN type indication message is defined;
During implementation of the embodiments of the present invention, the applicant finds that the following problems at least exist in the prior art:
If the CA is not taken into account and both Uu interface and Un interface only support a cell, CC/cell allocation of Un and Uu interfaces will not exist. The DeNB can work normally after determining whether it is necessary to configure the BH subframe according to the RN type after acquiring the RN type.
If the CA is taken into considered, the problem will be complicated. The cell that can be accessed to some RNs in Un interface may be not accessed owing to limit of the RN type. For example:
The RN accesses a DeNB1 for a RACH on cell a in Phase II for starting the RN. According to the cell list downloaded from the RN OAM in Phase I, the cells that can be used by the RN under the DeNB1 is cell a and cell b; meanwhile, the cell list of the Uu interface downloaded by the RN from the RN OAM comprises cell a, cell b and cell c. Thus, if the RN type reported by the RN to the DeNB is “Not requiring resource division”, the DeNB cannot work normally. The main reasons are as follows:
(1) The DeNB does not know whether the RN supports other cells besides cell a, so the DeNB cannot realize CA operation for the RN;
(2) The DeNB does not know which cells may be used by the RN Uu interface and whether resource division is required when these cells are combined with the cell of the Un interface;
In conclusion, in order to ensure that the system combining the CA and the RN can work normally, it is necessary to solve the above problems; however, such technical solution has not been provided in prior art.